Abstract/Summary

Of all the characteristics of biodiversity, the most noteworthy
is its variability. Recognition that the significance
of the mechanisms underlying this variation
changes as the scale of interest is altered, and that
variation at one level may cascade up (or down) to affect
many others in the ecological and genealogical hierarchies,
are hallmarks of modern ecology (Wiens, 1989).
For example, it is clear that both local-andregional-scale
processes affect the identity and richness of species at
any given site (Ricklefs, 1987, 2004; Hawkins &
Porter, 2003; Witman et al., 2004; Kreft & Jetz, 2007)
and that local–regional interactions can profoundly
affect the properties of assemblages (Gaston, 2000;
Blackburn&Gaston, 2001a; Leibold et al., 2004; Rangel
& Diniz-Filho, 2005; Thomas et al., 2008), even in
circumstances where life history characteristics have
little influence over the demographic rates of their
constituent species (Hubbell, 2001;He, 2005). Likewise,
genetic-level variation in primary producers can
cascade up through individuals to affect the functioning
of whole ecosystems, including feedback loops to plant
performance (Treseder & Vitousek 2001; Whitham
et al., 2003). For example, genetic variation among
pinyon pines in resistance to a stem-boring moth, whose
feeding activity on susceptible pines can lead to cone
elimination, has effects on seed-feeding birds and mammals,
and also on fungi in the decomposer community
(Whitham et al., 2003). In consequence, understanding
the determinants of biodiversity requires investigation of
processes at a variety of spatial and temporal scales and,
as a first step, the identification of the patterns which are the reflection, though sometimes beguiling, of these
processes (Gaston & Blackburn, 1999). Doing so is
essential, not only because of the insight into the natural
world that such understanding brings, but also because
it is only in this way that appropriate interventions can
be recommended to slow the extraordinary impact humansare
havingonregionalandglobal diversity (Brooks
et al., 2002; Thomas et al., 2004; Gaston, 2005;Chown
& Gaston, 2008; Butchart et al., 2010).